Eric C. Strauss disclosed an automatic protracting and locking hypodermic needle guard in his U.S. Pat. No. 4,664,654 comprising a sliding member 16 and a stationary member 28. Even the protrusions 24 can be engaged with the bevel shaped indention 37 to lock the needle tube 42, 41 within the sliding member 16 for its disposal. However, if the two protrusions 24 are accidentally compressed to disengage from the intention 37, the spring 30 will urge the needle 41 outwardly to cause injury or contamination to a nurse, a patient or anyone else.
Edward Klein disclosed a disposable safety medical syringe in his U.S. Pat. No. 4,955,868 by providing a shield wall 4 for protecting the hypodermic needle 1 within the wall 4. However, the shield wall 4 is resiliently urged outwardly by the spring 2, which will be easily compressed to retract the wall 4 inwardly to protrude the needle tip outwardly to still possibly cause injury or contamination accident. Besides, the shield wall 4 has a diameter larger than a diameter of the syringe wall 11 and the wall 4 has its front end portion provided with the shield opening 6 always urged by the spring 2 so that a puncture of the needle 1 will always be obstructed by the shield wall 4, thereby influencing a precise puncture on a patient skin for his or her medical treatment.
As shown in FIG. 6, a conventional syringe 1 includes a needle means 2 having a needle holder 22 secured with an adapter 11 of the syringe 1 and a needle 21 stored in a needle sleeve 5 having a central hole 52 formed in the sleeve 51. The needle 21 after being used can be easily withdrawn to cause contamination or injury to the others.
The present inventor has found the drawbacks of the conventional syringes, and invented the present safety syringe with single use.